My 92 1/2 recently started lighting up the brake warning light about 2 minutes into each trip. My pedal feels the same as it always did, straight to the floor....(JUST JOKING!) No but really, I have played with the brake release handle, checked for fluid leaks. All okay. Is my master cylinder beginning to fail?

 

of course, fluid level is fine?

 

unplug the electrical connection at the master cylinder and plug it back in. It should have rear wheel abs that may reset it.

 

Fluid is good. When I first got the truck I had to top it off a couple of times, but where ever it was leaking it quit. But that was a year ago.